Young children\u27s written response to text

Although elementary teachers are encouraged to use reader response strategies in their work with children, many questions remain about the nature of young children\u27s response. This study is part of a year-long naturalistic exploration of second and third grade students\u27 written responses to text. Entries from children\u27s reading logs constituted the primary data source for this study. Analysis focused on two different assignments or writing tasks: Write what you remember and \u27Write what you think or feel. The children responded to four different types of texts (two per task). Task and text differences were found in children\u27s personal statements, the nature of those personal statements, and the relationship between children\u27s written statements and information from the text

Aging of dissolved copper and copper-based nanoparticles in five different soils: short-term kinetics vs long-term fate

With the growing availability and use of copper based nanomaterials (Cu-NMs), there is increasing concern regarding their release and potential impact on the environment. In this study, the short term (≤ 5 days) ageing profile and the long term (4 months) speciation of dissolved Cu, copper oxide (CuO-) and copper sulfide nanoparticles (CuS-NPs) were investigated in five different soils using X-ray absorption spectroscopy (XAS). Soil pH was found to strongly influence the short term chemistry of the Cu-NMs added at 100 mg/kg above background. Low pH soils promoted rapid dissolution of CuO-NPs that effectively aligned their behaviour to that of dissolved Cu within 3 days. In higher pH soils, CuO-NPs persisted longer due to slower dissolution in the soil and resulted in contrasting short term speciation compared to dissolved Cu, which formed copper hydroxides and carbonates that were reflective of the soil chemistry. Organic matter appeared to slow the dissolution process but in the long term, the speciation of Cu added as dissolved Cu, CuO-NPs and CuS-NPs were found to be same for each soil. The results imply that in the short term Cu-NMs may exhibit unique behaviour in alkaline soils compared to their conventional forms (e.g. in the event of an adverse leaching event), but in the long term (≥ 4 months), their fates are dictated by the soil properties and are independent of the initial Cu form, and are likely to present minimal risk of nano-specific Cu-NM impact in the soil environment for the concentration studied here

Mitigating seismic risk in developing countries: A case study on the 2005 Kashmir earthquake

The increase in awareness and understanding of earthquakes has encouraged the development of culturally appropriate risk mitigation strategies that aim to build community resilience in preparation for the next natural disaster. In response to the magnitude M W 7.6 earthquake that struck the Kashmir region of northern Pakistan and the large number of residential housing collapses in Pakistan, an analytical investigation was performed on a damaged concrete building and prototype housing structures to evaluate this performance against seismic risk. The reconstruction efforts in Pakistan following the earthquake and the findings of this study are discussed with the aim of mitigating seismic risk in all developing countries. Results suggest that modifications to building layout and simple seismic resistance techniques for single and multi-storey structures, such as the reorientation of columns and the use of seismic banding, can considerably improve the performance of structures, with little or no additional cost

Determination of the effect of gas viscosity upon gas flow in permeable media containing water and gas

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Bibliography: p. 51-53.Not availabl

Effects of Transformations of Ag and CuO Nanoparticles on Their Fate in Freshwater Wetland Sediments and Plants

Engineered nanomaterials (ENMs) are increasing becoming incorporated into consumer products to imbue remarkable physical and chemical properties. The increased use of these ENMs leads to a growing need to understand the environmental fate of ENMs after release. Many ENMs, including Ag and Cu ENMs, have the potential to undergo complex physical and chemical transformations which impact their toxicity, solubility and fate in the environment. There is a lack of research characterizing the transformation rate and understanding how these transformations affect interactions with organisms and the ultimate environmental fate. The first objective of this thesis was to understand how transformations of Ag ENMs affect the uptake, distribution and speciation of these materials in plants. Terrestrial (alfalfa, Medicago sativa) and an aquatic (duckweed, Landoltia punctate) plant species were exposed hydroponically to as manufactured (“pristine”) Ag0-NPs and more environmentally relevant (“transformed”) Ag2S NPs. The uptake, spatial distribution and speciation of Ag were analyzed using synchrotron based X-ray Absorption Spectroscopy (XAS) techniques to provide mechanistic insights into the uptake of these ENMs. The reduced solubility and reactivity of Ag2S ENMs was expected to prevent plants from solubilizing these particles and only allow for direct uptake of particles. For the more soluble Ag species, the absorption of Ag+ ions was expected to be primarily the mechanism of Ag uptake. Although the total Ag associated with the plants was similar, the Ag distribution in the roots was dramatically different. The transformed ENMs (Ag2S) appeared to be taken into the plant tissue as sulfidized ENMs. The pristine Ag0 ENMs were found to partially dissolve and incorporate into the plant tissue as both dissolved Ag and Ag0-NPs. The fact that ENMs readily attach onto plant tissue regardless of speciation and solubility suggests that exposure to ENMs may be controlled by factors affecting attachment to root surfaces. However, internalization of Ag appears to be affected by solubility. The second objective was to characterize the impact of transformations of Ag and Cu-based ENMs on the distribution, speciation and fate of these materials in subaquatic sediments and the aquatic plant, E. Densa in a simulated emergent freshwater wetland using large-scale mesocosms. The exposure of pristine (Ag0 and CuO) ENMs and their transformed analogues (Ag2S and CuS) was compared to an ionic control (Cu(NO3)2) to determine if nanoparticulate species of metals were distributed differently than their dissolved counterparts. The metal speciation was determined using XAS to elucidate relative timescales of transformations. The pristine ENMs were expected to rapidly transform into their more stable sulfidized species and the uptake of Ag and Cu were expected to depend on the solubility of the ENMs. Transformations of the pristine ENMs were found to be rapid (weeks) in the surficial sediment, but slower (months) in the aquatic plant tissue. The uptake of ENMs coupled with the slow transformation in the aquatic plant tissue suggests ENMs persist longer than the timescales measured in sediments. This knowledge enables better risk forecasting for ENMs exposed to aquatic organisms and informs toxicity testing to ensure correct forms of ENMs are examined. This thesis provided several novel contributions to the understanding of how transformations of ENMs affect their interactions with plants and their fate in real complex environments. Mechanistic insights into the attachment and uptake of ENMs into plant tissues were identified suggesting two predominant uptake pathways. Relative timescales of ENM transformations in freshwater wetland sediments and plant tissue provided suggests plants can slow transformations and allow labile ENMs to persist longer than assumed.</p

Effect of Initial Speciation of Copper- and Silver-Based Nanoparticles on Their Long-Term Fate and Phytoavailability in Freshwater Wetland Mesocosms

International audienc